1. Field of Invention
The present invention relates to communication signal detecting circuit, and more particularly to a high frequency regenerative direct detector, which can not only reduce radio interference to provide a better voice clarity but also exempt the limitation of Federal Communication Commission (FCC), so as to provide a longer remote control distance for the radio frequency (RF) consumer products and devices while being cost effectively.
2. Description of Related Arts
Nowadays, radio frequency has been widely in use for enhancing the mobility of a product. By simply employing a receiver and a transmitter, a user is able to remote control the product from a predetermined distance. The distinctive feature of the radio frequency is that when a higher radio frequency is used, a longer remote control distance can be obtained. Therefore, a high end product such as a cellular phone must be utilized at least 900 MHz in order to receive the signal from the transmitter to the receiver within a long remote control distance. Also, for the low end product such as home appliance or alarm system, a lower radio frequency may be utilized.
It is ideal that every single product utilizes a higher radio frequency so that the user is able to remote control the product more precisely in a distant manner. However, to utilize higher radio frequency in a product has several drawbacks generally. FIG. 1 illustrates a partial schematic circuit diagram for a 900 MHz cellular phone RF receiver that illustrates the complexity of such circuit. The Super-heterodyne circuit specifically incorporated with the cellular phone comprises a RF amplifier for amplify the incoming band signal such as 935 to 960 MHz, a local oscillator which frequency is tuned below the 900 MHz incoming signal frequency is injected into a mixer. The output of the mixer, intermediate frequency at 135 MHz, is amplified and inputted to an intermediate frequency processor chip. Even though the Super-heterodyne circuit provides a good performance, the circuit configuration for the receiver is relatively complicated and expensive.
As shown in FIG. 2, a circuit utilizing with 900 MHz radio frequency for an existing home use cordless phone is illustrated, wherein the circuit, which is another type of Super-heterodyne circuit, also must comprise the basic components, such as the RF amplifier, the local oscillator, the mixer, the IF amplifier, and the IF processor chip. Even through the circuit configuration for the cordless home phone is simple than the Super-heterodyne circuit of the cellular phone, the cost of the circuit is still expensive and complicated enough that the most common mid/low end products are not affordable.
In order to reduce the cost of the product, a lower radio frequency has to use. For example, the receiver and transmitter for an existing remote control toy car can only afford to utilize a radio frequency in a range from 27 to 49 MHz. However, the circuit efficiency is low and radio interference is high. Besides, the transmitter output power is limited ⅕ in comparison with the 900 MHz per FCC regulation. Hence, the remote control distance is short and a long exposed antenna is required due to the longer wavelength.
Another example illustrates that the circuit for an existing remote control alarm guard device utilizes a 300 MHz radio receiver. Since the transmitter output power is about xe2x85x9 in comparison with the 900 MHz per FCC regulation, the remote control distance for the alarm guard device is relatively short. Furthermore, the continuous transmission from the transmitter to the receiver for supervision is not allowed per FCC regulation, which will substantially decrease the accuracy and the efficiency of remote control of the product.
A main object of the present invention is to provide a high frequency regenerative direct detector, which can reduce radio interference to provide a better voice clarity, so as to provide a longer remote control distance for the radio frequency (RF) consumer products and devices while being cost effective.
Another object of the present invention is to provide a high frequency regenerative direct detector, which comprises a superior radio frequency (RF) transistor for directly detecting out the human being audible frequency, so as to simplify the circuit configuration of the present invention that significantly reduces the cost and pros ides a better performance.
Another object of the present invention is to provide a high frequency regenerative direct detector, which exempts the limitation of Federal Communication Commission (FCC) part 15 for radio frequency device above 70 MHz that continuous transmission is not allowed except 900 MHz band from 902 MHz to 928 MHz or some other band at 2.4 GHz and above.
Another object of the present invention is to provide a high frequency regenerative direct detector, wherein the receiver is employed with a radio frequency detection circuit for amplification, signal mixing and detection of designated incoming RF signal. The audio modulation frequency still be detected out directly through the circuitry. Once the modulation frequency signal is detected out, the user can use the audio band signal or codes (depending on the type of the transmitter) to conduct a desired output for the product such as voice communication, control motor movement or alarm triggering.
Another object of the present invention is to provide a high frequency regenerative direct detector, wherein no expensive or complicated circuit structure is required to employ in the present invention in order to achieve the above mentioned objects. Therefore, the present invention successfully provides an economic and efficient solution for providing a circuit configuration with a higher radio frequency for the mid/low end wireless products such as remote control security, walkie talkie or alarm guard system without using expensive and complicated Super-heterodyne circuit.
Accordingly, in order to accomplish the above objects, the present invention provides a high frequency regenerative direct detector, which comprises a power supply and a signal detecting circuit arrangement electrically connected thereto.
The signal detecting circuit arrangement, which is a transistor control system, comprises a high frequency by-pass circuit, a LC tank circuit configured to be tuned at a pre-tuned frequency to receive an incoming signal and to generate an oscillator frequency ranging from 850 MHz to 960 MHz, a quenching circuit generating a quenching frequency, and a transistor circuit device configured to incorporate the oscillator frequency into the quenching frequency in such a manner that when the incoming signal matches the pre-tuned frequency, a timing to achieve a saturated level of the quenching frequency is faster than no signal period, and a modulation frequency of the incoming signal is detected out from the signal detecting circuit arrangement.